The present invention is related to communication exchange systems in general and is particularly connected with the communication exchange system in a general digital integrated network.
So far, telegraphic type and telephone type of exchange systems have been studied and developed independently of each other.
Telegraphic type exchange systems may be mainly classified into circuit exchange system and store-and-forward exchanger systems. A packet exchange system stands between the two.
The circuit exchange system is appropriate for conversational type of communications but utilization of the transmission line is very inefficient.
The store-and-forward exchange system is efficient in terms of line utilization but is not appropriate for conversational communication.
A packet exchange system is, in principle, a type of a store-and-forward exchange system by which data is transmitted in a unit called a packet. This system maintains utilization efficiency of the line and is also applicable to conversational communication if a certain extent of time lag is tolerated. This, of couse, is referring to a conversational communication in the telegraphic system and not the conversational communication in the telephone system.
On the other hand, the telephone type of exchange system has been employing a system which is very similar to the circuit exchange system mentioned above, supported by the absolute necessity of securing conversational type of communications. Therefore, utilization rate of the line is very poor.
Introduction of multiplex communication into the transmission line in order to improve the line utilization rate and the TASI (Time Assignment Speech Interpolation) aiming at increased utilization rate of communications between two points taking advantage of redundancy of conversation are known so far. However, efforts to secure conversational type of communication while at the same time to attempt to improve utilization rate of the line through integration of both the transmission line and the exchange have not been made.